CN108816294B

CN108816294B - Fixed bed Fischer-Tropsch iron catalyst activation pretreatment method

Info

Publication number: CN108816294B
Application number: CN201810643929.4A
Authority: CN
Inventors: 石玉林; 王涛
Original assignee: Pujiang Sixintong Technology Co ltd
Current assignee: Zhejiang Sixintong Hydrogen Energy Technology Co ltd
Priority date: 2018-06-21
Filing date: 2018-06-21
Publication date: 2021-04-02
Anticipated expiration: 2038-06-21
Also published as: CN108816294A

Abstract

The invention provides a fixed bed Fischer-Tropsch iron catalyst activation pretreatment method, which comprises the following steps: 1) filling an iron-based catalyst into a catalyst bed layer; 2) the temperature is raised to 160-plus-195 ℃, hydrogen is used as reducing gas, and the space velocity is 1000-plus-3000 h^‑1(ii) a Then adjusting the reducing gas to H₂the/CO is 30-50, the temperature is increased to 240 ℃ and the constant temperature is kept for 4-10 h; then the temperature is raised to 245 ℃ and 250 ℃, and the constant temperature is kept for 4-10 h; 3) heating to 250-265 deg.C, and regulating the reducing gas to H₂CO 20-30, reducing for 6-12 h; detecting the volume concentration of CO, and entering a step 4) if the volume concentration of CO is lower than 0.5-0.7%; if the content is higher than 0.5-0.7%, continuously reducing to be lower than 0.5-0.7%; 4) adjusting the reducing gas to H₂CO 10-20, reducing for 4-10 h; detecting the volume concentration of CO, and entering the step 5) if the volume concentration of CO is lower than 0.7-1.3%; if the content is higher than 0.7-1.3%, continuously reducing to be lower than 0.7-1.3%; 5) adjusting the reducing gas to H₂/N₂Reducing for 4-8h at 10-20 deg.

Description

Fixed bed Fischer-Tropsch iron catalyst activation pretreatment method

Technical Field

The invention relates to an on-line activation pretreatment method for a Fischer-Tropsch iron-based catalyst applied to a fixed bed reactor.

Background

The Fischer-Tropsch synthesis reaction is to synthesize gas (H)₂And CO) at a temperature and pressure to produce hydrocarbon products (both liquid and solid) over the catalyst. The synthesis gas can be prepared from carbonaceous raw materials such as coal, natural gas, coal bed gas, shale gas or biomass. As petroleum resources are increasingly tense, Fischer-Tropsch synthesis reactions are receiving wide attention from researchers in various countries around the world. Generally speaking, the fischer-tropsch synthesis reaction involves the main chemical reaction formula:

nCO+(2n+1)H₂→C_nH_2n+2+nH₂O (1)

nCO+(2n)H₂→C_nH_2n+nH₂O (2)

CO+H₂O→CO₂+H₂ (3)

the Fischer-Tropsch synthesis catalyst is divided into an iron-based catalyst and a cobalt-based catalyst, wherein the iron-based catalyst has lower cost and better water gas shift reaction activity and can be applied to H₂The synthesis gas has wider CO range, so the synthesis gas has more industrial application value. The Fischer-Tropsch catalyst must be activated (or reduced) before use to be active, and the activation of the Fischer-Tropsch catalyst can be represented by the following reaction formula:

Fe₂O₃+CO+H₂→Fe_xC_y+CO₂+H₂O (4)

Fe₂O₃+H₂→α-Fe+H₂O (5)

Co₃O₄+H₂→Co+H₂O (6)

after the iron-based catalyst and the cobalt-based catalyst are activated, the catalytic active phase is respectively changed into Fe₃O₄、ɑ-Fe、Fe_xC_yAnd elemental Co. The crystal phase composition of the catalyst and the reaction performance can be changed according to different activation conditions.

Fischer-Tropsch synthesis reactors generally have three main forms, namely a fluidized bed, a slurry bed and a fixed bed. The fluidized bed reactor is generally operated at high temperature, and only Sasol in south Africa has industrial application at present due to complex operation, large abrasion of the catalyst and easy carbon deposition and blockage. The slurry bed reactor is widely applied to large industrial devices due to uniform mixing, good heat transfer effect, convenient temperature control and easy amplification, but has the problems of more internal components, difficult liquid-solid separation caused by serious abrasion, high requirement on catalyst granularity and the like. The fixed bed reactor has the characteristics of flexible and various forms, simple operation and the like, and is very suitable for small and medium Fischer-Tropsch synthesis devices. The well-known Arge and SMDS processes are based on fixed bed reactors. However, the fixed bed reactor has poor heat and mass transfer, which easily causes the catalyst to generate 'hot spots' and even sinter, and collects water in the catalyst, resulting in the reduction of the catalyst activity.

Chinese patent application CN201510641043.2 provides a reduction method of fischer-tropsch iron based catalyst: (1) the constant temperature is kept for 3-10h at the beginning of reduction (220-; (2) more than 50 percent of inert gas is added into the reducing gas, and the defects that the size of the reduction reactor becomes very large and the cost is high due to a large amount of inert gas; (3) CO removal from circulating gas₂And H₂O to reduce its oxidation. But CO produced during the reduction process₂And H₂The amount of O is not so large that the process is economically disadvantageous in industrial use.

Chinese patent applications CN103084219A and CN201310043997.4 provide similar reduction methods for fischer-tropsch synthesis iron-based catalysts: the conventional synthesis gas is replaced by the mixed gas of hydrogen and gaseous hydrocarbon, namely, the carbon atoms are provided by replacing CO with the gaseous hydrocarbon (C1-C4), the carbon deposition is reduced, but the reduction performance of the gaseous hydrocarbon is not as good as that of CO, and the reduction effect is general.

In conclusion, how to develop an activation pretreatment method of a fixed bed Fischer-Tropsch iron catalyst which is not easy to generate 'hot spots' and has good reduction effect is one of the technical problems to be solved in the field.

Disclosure of Invention

The invention provides an activation pretreatment method of a fixed bed Fischer-Tropsch iron catalyst for making up the defects in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides an activation pretreatment method of a fixed bed Fischer-Tropsch iron catalyst, which comprises the following steps:

1) filling an iron-based catalyst into a catalyst bed layer of a fixed bed reactor, wherein the filling quality of the iron-based catalyst in the catalyst bed layer is gradually increased along the flowing direction of synthesis gas;

2) gradually raising the reduction temperature to 160-195 ℃, and in the process of raising the temperatureHydrogen is reducing gas, and the space velocity is 1000-3000h^-1(ii) a After the temperature is raised to 160-195 ℃, the reducing gas is adjusted to H₂The volume ratio of the CO and the mixed gas is 30-50, and the space velocity is 1000-^-1Gradually raising the temperature to 210-240 ℃; after the temperature is increased to 210 ℃ and 240 ℃, keeping the temperature for 4-10 h; then gradually raising the temperature to 245 ℃ and 250 ℃, and keeping the temperature for 4-10 h;

3) gradually raising the reduction temperature to 250-265 ℃, and adjusting the reduction gas to H₂The volume ratio of the CO and the mixed gas is 20-30, and the space velocity is 2000-3000h^-1Reducing for 6-12 h; detecting the volume concentration of CO at the gas material outlet of the fixed bed reactor, and entering the step 4 if the volume concentration of CO is lower than 0.5-0.7 percent; if the concentration is higher than 0.5-0.7%, continuing reduction (for example, continuing reduction for 4-10h) until the CO volume concentration is lower than 0.5-0.7%, and then entering step 4);

4) adjusting the reducing gas to H₂The volume ratio of the CO and the mixed gas is 10-20, and the space velocity is 4000-^-1Reducing for 4-10 h; then detecting the volume concentration of CO at the gas material outlet of the fixed bed reactor, and entering the step 5) if the volume concentration is lower than 0.7-1.3%; if the concentration is higher than 0.7-1.3%, continuing reduction (for example, continuing reduction for 2-8h) until the CO volume concentration is lower than 0.7-1.3%, and then entering step 5);

5) adjusting the reducing gas to H₂And N₂The volume ratio of (1) is 10-20, and the reduction is carried out for 4-8 h.

According to the activation method, when the iron-based catalyst is filled, the filling quality of the iron-based catalyst in a catalyst bed layer is gradually increased along the flowing direction of the synthesis gas, so that the amount of the catalyst close to an inlet of the synthesis gas is small, and the heat release is stable; as the reaction proceeds, the partial pressure of the synthesis gas is reduced, and although the loading of the catalyst is gradually increased, the reaction heat is stable and controllable, so that the temperature gradient of the whole catalyst bed is smaller. In some preferred embodiments of the present invention, the catalyst bed layer is equally divided into n sections along the flow direction of the synthesis gas, the section near the synthesis gas inlet is taken as the 1 st section, the 2 nd section to the nth section are sequentially arranged along the flow direction of the synthesis gas, and the catalyst loading mass M of the 2 nd section₂As a catalyst in stage 1Filling mass M₁1.2-2.5 times of; by analogy, the catalyst loading mass M of the nth stage_nFor the catalyst loading mass M of section n-1_n-11.2-2.5 times of; and n is an integer of 4-12. The catalyst bed layer is equally divided into a plurality of sections, and 1.2-2.5 times of catalyst is filled in the catalyst bed layer in an increasing proportion, so that hot spots of the catalyst can be effectively avoided, the temperature gradient of the catalyst bed layer is reduced, the catalyst activation effect is better, and the higher activity of the catalyst is ensured. More preferably, said M₂Is M₁1.4-to 2.0-fold of (A), said M_nIs M_n-11.4-2.0 times of the catalyst bed, so that the reaction heat is more stable and controllable, the temperature gradient of the catalyst bed is smaller, and the catalytic performance is better.

Optionally, in some embodiments, the catalyst bed may also be packed with inert solid particles, such as quartz sand, etc., and the inert solid particles and the catalyst are mixed to act as a catalyst dilution function, for example, each or some of the packing sections in the catalyst bed may be packed with some inert solid particles. In general, in a pilot plant, it is preferable to add inert solid particles such as silica sand to dilute the catalyst, for example, silica sand may be loaded to make the sum of the loading quality of silica sand and catalyst equal in each section, but not limited to this loading mode.

In the activation method of the invention, in the step 2), the reduction temperature is gradually increased to 160-^-1(ii) a After the temperature is raised to 160-195 ℃, the reducing gas is adjusted to H₂The volume ratio of the CO and the mixed gas is 30-50, and the space velocity is 1000-^-1Gradually raising the temperature to 210-240 ℃; after the temperature is increased to 210 ℃ and 240 ℃, keeping the temperature for 4-10 h; then gradually raising the temperature to 245 ℃ and 250 ℃, and keeping the temperature for 4-10 h; at this time, the catalyst starts to be activated, and the reduction is performed with a reducing gas having a high hydrogen-carbon ratio, which is advantageous for Fe₂O₃To Fe₃O₄The conversion of (2) and simultaneously slowing down the carbonization degree of the catalyst and reducing the generation of carbon on the surface of the catalyst. In some preferred embodiments of the present invention, in the step 2), in the process of gradually raising the temperature of the reduction reaction to 160-195 ℃, the temperature raising rate is controlled to be 10-25 ℃/h; in step 2)Gradually raising the temperature from 160-195 ℃ to 210-240 ℃ at a rate of 8-15 ℃/h; in the step 2), the temperature rise rate is controlled to be 5-10 ℃/h in the process of gradually raising the reduction temperature from 210-240 ℃ to 245-250 ℃. In the temperature rising process from 160-195 ℃ to 245-250 ℃, the catalyst is gradually activated, and the temperature rising rate is slowly reduced (from 10-25 ℃/h to 8-15 ℃/h and then to 5-10 ℃/h), which is beneficial to reducing the carbonization degree of the catalyst and reducing the generation of carbon deposition on the surface of the catalyst.

In the activation method of the invention, in the step 3), the reduction temperature is gradually increased to 250-₂The volume ratio of the CO and the mixed gas is 20-30, and the space velocity is 2000-3000h^-1Reducing for 6-12 h; the reduction is carried out by adopting reducing gas with low hydrogen-carbon ratio in the step, which is beneficial to FeC_xGenerating; after 6-12h of reduction, continuously maintaining the reduction condition, detecting the CO volume concentration at the gas material outlet of the fixed bed reactor, if the concentration is lower than 0.5-0.7%, ending the reduction condition, and entering the step 4); if the concentration is above 0.5-0.7%, the reduction under reducing conditions is continued until the CO volume concentration is below 0.5-0.7% (e.g. the reduction is continued for 4-10h) and the reducing conditions are ended, after which step 4 is entered). In some preferred embodiments of the present invention, in step 3), in the process of gradually increasing the reduction temperature to 250-265 ℃, the temperature increase rate is controlled to be 3-8 ℃/h, which is beneficial to reducing the carbonization degree of the catalyst and reducing the generation of carbon deposition on the surface of the catalyst.

The activation method of the present invention, step 4), is to adjust the reducing gas to H₂The volume ratio of the CO and the mixed gas is 10-20, and the space velocity is 4000-^-1Reducing for 4-10 h; in the step, the hydrogen-carbon ratio of the reducing gas is further reduced, the space velocity is increased, and the activity of the catalyst can be slowly released. After reduction is carried out for 4-10h, the reduction condition is continuously kept, the CO volume concentration at the gas material outlet of the fixed bed reactor is detected, if the concentration is lower than 0.7-1.3%, the reduction condition is ended, and the step 5) is carried out; if the concentration is above 0.7-1.3%, the reduction conditions are maintained and the reduction is continued until the CO volume concentration is below 0.7-1.3% (e.g. the reduction is continued for 2-8h), after which it is concludedThe reducing conditions are bundled and step 5) is entered.

In the activation method of the present invention, in step 5), the reducing gas is adjusted to H₂And N₂The volume ratio of (1) is 10-20, and the reduction is carried out for 4-8 h. In this step, N is used₂Replace CO and is beneficial to reducing CO in the initial stage of reaction₂And H₂The oxidation of O protects the catalyst just after activation. In some preferred embodiments of the present invention, in step 5), the space velocity of the reducing gas is 4000-^-1。

In preferred embodiments of the invention, the iron-based catalyst is a precipitated iron catalyst for fischer-tropsch synthesis, preferably in the form of microspheres, preferably having a particle size of 20 to 200 μm. The invention has no special requirements on the composition of the Fischer-Tropsch synthesis precipitated iron catalyst, and the Fischer-Tropsch synthesis precipitated iron catalyst commonly used in the field can be activated by adopting the method. In some embodiments of the invention, the fischer-tropsch synthesis precipitated iron catalyst is, for example, supported on alumina or silica, and supported on one or more of Na, K, Cu, Ru, and Mn; in some embodiments, the fischer-tropsch precipitated iron catalyst comprises a composition, for example in mass ratios, of iron: auxiliary agent: carrier (17-20): (0.5-6): (75-80); in some further preferred embodiments, the composition contains, in terms of mass ratio, iron: auxiliary agent: carrier (17-20): (1.0-5): (77-80); specifically, for example, the catalyst composition is, iron: auxiliary agent: carrier 18.1:1.9:79 (mass ratio), iron: auxiliary agent: carrier 17.2:2.8:80 (mass ratio) and the like.

In some preferred embodiments of the invention, the reduction is carried out at a pressure of 0.5 to 3.0MPa in each step.

The technical scheme provided by the invention has the following beneficial effects:

when the catalyst activated by the method is applied to the fixed bed Fischer-Tropsch synthesis reaction, the problem that the catalyst is easy to generate hot spots in the conventional fixed bed reactor can be solved.

Drawings

FIG. 1 is a schematic illustration of catalyst loading in one example.

The reference numbers in the figures illustrate: 1 is the 1 st section of the catalyst bed, 2 is the 2 nd section of the catalyst bed, 3 is the 3 rd section of the catalyst bed, 4 is the 4 th section of the catalyst bed, 5 is the 5 th section of the catalyst bed, and 6 is the catalyst; 7 is quartz sand.

Detailed Description

In order to better understand the technical solution of the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples. The detection methods in the following examples or comparative examples are all conventional detection methods in the field, and are not described in detail

Example 1

A fixed bed Fischer-Tropsch iron catalyst activation pretreatment method comprises the following steps:

1) a fixed bed reactor having a diameter of 10mm was charged with 0.5g of a Fischer-Tropsch iron catalyst (containing, in terms of mass ratio, Fe: Cu: K: Al)₂O₃18.1:1:1.9: 79). The whole catalyst bed layer is equally divided into 5 sections (see figure 1), one section close to the synthesis gas inlet of the fixed bed reactor is taken as the 1 st section, the 2 nd section to the 5 th section are sequentially arranged along the flow direction of the synthesis gas, and the 1 st section to the 5 th section are respectively filled with 0.03 g, 0.05 g, 0.09 g, 0.13 g and 0.20 g of catalyst and 1.37 g, 1.35 g, 1.31 g, 1.27 g and 1.20 g of quartz sand;

2) setting the reduction pressure to be 1.0 MPa; in the process of heating from normal temperature to 180 ℃, the heating rate is 20 ℃/H, and the reducing gas is H₂Airspeed of 2000h^-1(ii) a After the temperature is increased to 180 ℃, the heating rate is changed to 10 ℃/H, and the reducing gas is adjusted to be H₂Mixed gas with CO, H₂The volume ratio of/CO is 50, and the space velocity is 2000h^-1(ii) a And (3) keeping the temperature for 6h after the temperature is raised to 230 ℃, adjusting the heating rate to 8 ℃/h after the constant temperature is finished, raising the temperature to 245 ℃, and keeping the temperature for 6 h.

3) After the constant temperature is finished, the temperature is continuously increased to 250 ℃, the temperature increase rate is 4 ℃/H, and the reducing gas H is adjusted₂Volume ratio of/CO 30, space velocity of 2000h^-1Then, the conditions are maintained for reduction for 12 h. After the reduction is finished for 12h, the condition is continuously kept, the volume concentration of CO in tail gas at the outlet of the reduction reactor is analyzed by gas chromatography, and after 4h, the CO concentration in the tail gas is found to be 0.38%, and the reduction condition is finished.

4) Adjusting the reducing gas H₂The volume ratio of/CO is 15, and the space velocity is 5000h^-1Then, the conditions were maintained for reduction for 6 h. After 6h of reduction, the conditions were maintained, and the volume concentration of CO in the tail gas at the outlet of the reduction reactor was analyzed by gas chromatography, and after 2h, the CO concentration in the tail gas was found to be 0.65%, and the reduction conditions were ended.

5) Adjusting the reducing gas to pure H₂And N₂，H₂/N₂The volume ratio of (A) is 15, and the space velocity is 5000h^-1And keeping for 6 h. And (5) finishing the activation.

Example 2

1) to a fixed bed reactor having a diameter of 10mm, 1.0g of a Fischer-Tropsch iron catalyst (containing, by mass: fe, Cu, K, Al₂O₃17.2:1.2:1.6: 80). The whole catalyst bed layer is equally divided into 5 sections, one section close to the synthesis gas inlet of the fixed bed reactor is taken as a 1 st section, the sections are sequentially divided into 2 nd to 5 th sections along the flow direction of the synthesis gas, and the 1 st to 5 th sections are respectively filled with 0.06 g, 0.10 g, 0.18 g, 0.26 g and 0.40 g of catalyst and 2.74 g, 2.70 g, 2.62 g, 2.54 g and 2.40 g of quartz sand;

2) setting the reduction pressure to be 2.0 MPa; in the process of heating from normal temperature to 180 ℃, the heating rate is 15 ℃/H, and the reducing gas is H₂Airspeed of 1500h^-1(ii) a After the temperature is increased to 180 ℃, the heating rate is changed to 12 ℃/H, and the reducing gas is adjusted to be H₂Mixed gas with CO, H₂The volume ratio of/CO is 40, and the space velocity is 1500h^-1(ii) a And (3) keeping the temperature for 5h after the temperature is raised to 230 ℃, adjusting the heating rate to 5 ℃/h after the constant temperature is finished, raising the temperature to 245 ℃, and keeping the temperature for 6 h.

3) After the constant temperature is finished, the temperature is continuously increased to 260 ℃, the temperature increase rate is 3 ℃/H, and the reducing gas H is adjusted₂Volume ratio of/CO of 20Airspeed of 2500h^-1Then, the conditions are maintained for reduction for 10 h. After the reduction is finished for 10 hours, the condition is continuously kept, the volume concentration of CO in tail gas at the outlet of the reduction reactor is analyzed by gas chromatography, and after 8 hours, the CO concentration in the tail gas is found to be 0.41 percent, so that the reduction condition is finished.

4) Adjusting the reducing gas H₂The volume ratio of/CO is 12, and the space velocity is 5500h^-1Then, the conditions are maintained for 5h of reduction. After 5h of reduction, the conditions were maintained and the volume concentration of CO in the tail gas at the outlet of the reduction reactor was analyzed by gas chromatography, and after 4h, the CO concentration in the tail gas was found to be 0.70%, and the reduction conditions were ended.

5) Adjusting the reducing gas to pure H₂And N₂，H₂/N₂The volume ratio of (A) is 15, and the space velocity is 5500h^-1And keeping for 6 h. And (5) finishing the activation.

Example 3

1) to a fixed bed reactor having a diameter of 10mm, 1.0g of a Fischer-Tropsch iron catalyst (containing, by mass: fe, Cu, K, Na, SiO₂18:1.2:1.2:0.6: 79). The whole catalyst bed layer is equally divided into 7 sections, one section close to the synthesis gas inlet of the fixed bed reactor is taken as a 1 st section, and the 2 nd section to the 7 th section are sequentially arranged along the flow direction of the synthesis gas, the 1 st section to the 7 th section are respectively filled with 0.03 g, 0.047 g, 0.07 g, 0.10 g, 0.16 g, 0.24 g and 0.35 g of catalyst, and 1.68 g, 1.67 g, 1.64 g, 1.60 g, 1.56 g, 1.48 g and 1.36 g of quartz sand;

2) setting the reduction pressure to be 2.0 MPa; in the process of increasing the temperature from normal temperature to 190 ℃, the temperature rise rate is 20 ℃/H, and the reducing gas is H₂Airspeed of 2000h^-1(ii) a After the temperature is raised to 190 ℃, the heating rate is changed to 10 ℃/H, and the reducing gas is adjusted to be H₂Mixed gas with CO, H₂The volume ratio of/CO is 50, and the space velocity is 2000h^-1(ii) a And (3) keeping the temperature for 6h after the temperature is raised to 230 ℃, adjusting the heating rate to 8 ℃/h after the constant temperature is finished, raising the temperature to 245 ℃, and keeping the temperature for 6 h.

3) After the constant temperature is finished, the temperature is continuously increased to 250 ℃, the temperature increase rate is 4 ℃/H, and the reducing gas H is adjusted₂The volume ratio of/CO is 30, and the space velocity is 2000h^-1Then, the conditions are maintained for reduction for 12 h. After the reduction is finished for 12h, the condition is continuously kept, the volume concentration of CO in tail gas at the outlet of the reduction reactor is analyzed by gas chromatography, and after 3h, the CO concentration in the tail gas is found to be 0.37 percent, so that the reduction condition is finished.

The performance tests of the activated catalyst samples of example 1, example 2 and example 3 were carried out in a fixed bed reactor. The reaction temperature is 250 ℃, and the synthesis gas H₂The volume ratio of the carbon dioxide to the CO is 2:1, and the pressure is 2.3 MPa. After 20-40 hours from the start of the reaction, the catalyst activity tended to be stable (i.e., 4 hours of continuous activity data (CO conversion, CO)₂Selectivity and CH₄Selectivity) is less than 2%), at which point sampling analysis begins. The test time was 300 hours. Tables 1-3 show the results of the catalytic performance test after activation at 100h, 200h and 300h, respectively.

TABLE 1 Fischer-Tropsch iron catalyst Performance data (100h)

	Example 1	Examples2	Example 3
				CO conversion (%)	58.6	61.4	60.8
CO₂Selectivity (%)	22.4	22.8	23.0
				CH₄Selectivity (%)	1.8	1.9	1.9
Temperature difference in bed (. degree. C.)	1.8	2.0	2.2

TABLE 2 Fischer-Tropsch iron catalyst Performance data (200h)

TABLE 3 Fischer-Tropsch iron catalyst Performance data (300h)

As can be seen from the data in tables 1-3: the catalysts of examples 1-3 after activation have high activity (CO conversion), by-product (CO)₂And CH₄) Low selectivity. When the reaction time is close to 300h, the catalyst performance is still stable, and the stability of the activated catalyst is proved to be good. And the temperature difference of the catalyst bed layer is small, and the smaller temperature difference of the bed layer is still maintained along with the continuous reaction for 300 hours.

Comparative example 1

0.5g of a Fischer-Tropsch iron catalyst (containing, by mass, Fe: Cu: K: Al) was charged into a fixed bed reactor having a diameter of 10mm₂O₃18.1:1:1.9: 79). The whole catalyst bed layer is equally divided into 5 sections, and 0.1 g of catalyst and 1.3 g of quartz sand are filled in the first section to the fifth section;

setting the reduction pressure to be 1.0 MPa;

in the process of heating from normal temperature to 180 ℃, the heating rate is 20 ℃/H, and the reducing gas is H₂Airspeed of 2000h^-1(ii) a After the temperature is increased to 180 ℃, the heating rate is changed to 10 ℃/H, and the reducing gas is adjusted to be H₂Mixed gas with CO, H₂The volume ratio of/CO is 50, and the space velocity is 2000h^-1(ii) a And (3) keeping the temperature for 6h after the temperature is raised to 230 ℃, adjusting the heating rate to 8 ℃/h after the constant temperature is finished, raising the temperature to 245 ℃, and keeping the temperature for 6 h.

After the constant temperature is finished, the temperature is continuously increased to 250 ℃, the temperature increase rate is 4 ℃/H, and the reducing gas H is adjusted₂The volume ratio of/CO is 30, and the space velocity is 2000h^-1Then, the conditions are maintained for reduction for 12 h. After the reduction is finished for 12h, the condition is continuously kept, the volume concentration of CO in tail gas at the outlet of the reduction reactor is analyzed by gas chromatography, and after 4h, the CO concentration in the tail gas is found to be 0.31 percent, so that the reduction condition is finished.

Adjusting the reducing gas H₂The ratio of/CO is 15, and the space velocity is 5000h^-1Then, the conditions were maintained for reduction for 6 h. After 6h of reduction, the conditions were maintained, and the volume concentration of CO in the tail gas at the outlet of the reduction reactor was analyzed by gas chromatography, and after 2h, the CO concentration in the tail gas was found to be 0.60%, and the reduction conditions were ended.

Adjusting the reducing gas to pure H₂And N₂，H₂/N₂The volume ratio is 15, and the space velocity is 5000h^-1And keeping for 6 h. And (5) finishing the activation.

Comparative example 1 performance testing of the activated catalyst sample was conducted in a fixed bed reactor. The reaction temperature is 250 ℃, and the synthesis gas H₂The volume ratio of the carbon dioxide to the CO is 2:1, and the pressure is 2.3 MPa. After 20-40 hours from the start of the reaction, the catalyst activity tended to stabilize (i.e., the Relative Standard Deviation (RSD) of the activity data was less than 2% for 4 consecutive hours), at which point sampling analysis was initiated. Table 4 shows the results of the catalytic performance test after activation (100 h).

TABLE 4 Fischer-Tropsch iron catalyst Performance data for comparative example 1

CO conversion (%)	59.0
		CO₂Selectivity (%)	24.5
CH₄Selectivity (%)	2.4
		Temperature difference in bed (. degree. C.)	2.7

The data in table 4 show that: in comparison with example 1, the catalyst of comparative example 1 has comparable activity (CO conversion) but by-product (CO) during the course of the comparative example being continued₂And CH₄) The selectivity is obviously higher, and the temperature difference of the bed layer is larger.

Comparative example 2

3) After the constant temperature is finished, the temperature is continuously increased to 260 ℃, the temperature increase rate is 3 ℃/H, and the reducing gas H is adjusted₂The volume ratio of/CO is 20, and the space velocity is 1500h^-1Then, the conditions are maintained for reduction for 10 h. After the reduction is finished for 10 hours, the condition is continuously kept, the volume concentration of CO in tail gas at the outlet of the reduction reactor is analyzed by gas chromatography, and after 9 hours, the CO concentration in the tail gas is found to be 0.45 percent, so that the reduction condition is finished.

4) Adjusting the reducing gas H₂The volume ratio of/CO is 12, and the space velocity is 1500h^-1Then, the conditions are maintained for 5h of reduction. After 5h of reduction, the conditions were maintained and the analysis of the CO concentration in the tail gas at the outlet of the reduction reactor was started by gas chromatography, and after 5h, the CO concentration in the tail gas was found to be 0.68%, and the reduction conditions were ended.

5) Adjusting the reducing gas to pure H₂And N₂，H₂/N₂The volume ratio of (A) is 15, and the space velocity is 1500h^-1And keeping for 6 h. And (5) finishing the activation.

Comparative example 2 activated catalystSample performance testing was performed in a fixed bed reactor. The reaction temperature is 250 ℃, and the synthesis gas H₂The volume ratio of the carbon dioxide to the CO is 2:1, and the pressure is 2.3 MPa. After 20-40 hours from the start of the reaction, the catalyst activity tended to stabilize (i.e., the Relative Standard Deviation (RSD) of the activity data was less than 2% for 4 consecutive hours), at which point sampling analysis was initiated. Table 5 shows the results of the catalytic performance test after activation (100 h).

TABLE 5 Fischer-Tropsch iron catalyst Performance data for comparative example 2

CO conversion (%)	52.3
		CO₂Selectivity (%)	27.2
CH₄Selectivity (%)	2.9
		Temperature difference in bed (. degree. C.)	3.5

The data in table 5 show that: the catalyst of comparative example 2 had lower activity (CO conversion) and by-product (CO) during the continuous run compared to example 2₂And CH₄) The selectivity is obviously higher, and the temperature difference of the bed layer is larger.

It will be appreciated by those skilled in the art that modifications or adaptations to the invention may be made in light of the teachings of the present specification. Such modifications or adaptations are intended to be within the scope of the present invention as defined in the claims.

Claims

1. A fixed bed Fischer-Tropsch iron catalyst activation pretreatment method is characterized by comprising the following steps:

2) gradually raising the reduction temperature to 160-195 ℃, and taking H in the process of raising the temperature₂The space velocity is 1000-3000h for reducing gas^-1(ii) a After the temperature is raised to 160-195 ℃, the reducing gas is adjusted to H₂The volume ratio of the CO and the mixed gas is 30-50, and the space velocity is 1000-^-1Gradually raising the temperature to 210-240 ℃; after the temperature is increased to 210 ℃ and 240 ℃, keeping the temperature for 4-10 h; then gradually raising the temperature to 245 ℃ and 250 ℃, and keeping the temperature for 4-10 h;

3) gradually raising the reduction temperature to 250-265 ℃, and adjusting the reduction gas to H₂The volume ratio of the CO and the mixed gas is 20-30, and the space velocity is 2000-3000h^-1Reducing for 6-12 h; detecting the volume concentration of CO at the gas material outlet of the fixed bed reactor, and entering the step 4) if the volume concentration is lower than 0.7 percent; if the concentration is higher than 0.7%, continuing to reduce the CO volume concentration to be lower than 0.7%, and then entering step 4);

4) adjusting the reducing gas to H₂The volume ratio of the CO and the mixed gas is 10-20, and the space velocity is 4000-^-1Reducing for 4-10 h; then detecting the volume concentration of CO at the gas material outlet of the fixed bed reactor, and entering the step 5) if the volume concentration is lower than 1.3 percent; if the concentration is higher than 1.3%, continuing to reduce the CO volume concentration to be lower than 1.3%, and then entering step 5);

2. The activation pretreatment method of fixed bed Fischer-Tropsch iron catalyst according to claim 1, wherein in the step 1), the catalyst bed is equally divided into n sections along the flow direction of the synthesis gas, and the section near the inlet of the synthesis gas is taken as the 1 st section, and the sections are sequentially arranged along the flow direction of the synthesis gasCatalyst loading mass M for stages 2 to n, 2₂For the catalyst loading mass M of stage 1₁1.2-2.5 times of; by analogy, the catalyst loading mass M of the nth stage_nFor the catalyst loading mass M of section n-1_n-11.2-2.5 times of; and n is an integer of 4-12.

3. The fixed bed fischer-tropsch iron catalyst activation pretreatment process of claim 2, wherein M is₂Is M₁1.4-to 2.0-fold of (A), said M_nIs M_n-11.4-2.0 times of the total weight of the composition.

4. The fixed bed Fischer-Tropsch iron catalyst activation pretreatment method of claim 3,

in the step 2), the temperature rising rate is controlled to be 10-25 ℃/h in the process of gradually rising the reduction temperature to 160-195 ℃;

in the step 2), the temperature rising rate is controlled to be 8-15 ℃/h in the process of gradually rising the reduction temperature from 160-195 ℃ to 210-240 ℃;

in the step 2), the temperature rise rate is controlled to be 5-10 ℃/h in the process of gradually raising the reduction temperature from 210-240 ℃ to 245-250 ℃.

5. The activation pretreatment method of fixed bed Fischer-Tropsch iron catalyst as claimed in claim 4, wherein in the step 3), the temperature rising rate is controlled to be 3-8 ℃/h in the process of gradually raising the temperature of the reduction to 250-265 ℃.

6. The activation pretreatment method of fixed bed Fischer-Tropsch iron catalyst as claimed in claim 5, wherein, in the step 5), the space velocity of the reducing gas is 4000-^-1。

7. The activation pretreatment method of fixed bed fischer-tropsch iron catalyst according to claim 6, wherein the iron based catalyst is a fischer-tropsch synthesis precipitated iron catalyst.

8. The activation pretreatment method of fixed bed Fischer-Tropsch iron catalyst according to claim 7, wherein the Fischer-Tropsch synthesis precipitated iron catalyst is microspherical and has a particle size of 20 to 200 μm.

9. The activation pretreatment method of fixed bed Fischer-Tropsch iron catalyst according to claim 7 or 8, characterized in that the Fischer-Tropsch synthesis precipitated iron catalyst takes alumina or silica as a carrier and one or more of Na, K, Cu, Ru and Mn as an auxiliary agent; the Fischer-Tropsch synthesis precipitated iron catalyst comprises the following components in percentage by mass (17-20): (0.5-6): (75-80) iron, an auxiliary agent and a carrier.

10. The activation pretreatment method for fixed bed fischer-tropsch iron catalyst according to claim 9, wherein the catalyst bed is further packed with inert solid particles for diluting the catalyst;

the reduction pressure in the reduction of each step is 0.5-3.0 MPa.

11. The fixed bed fischer-tropsch iron catalyst activation pretreatment process of claim 10, wherein the inert solid particles are silica sand.

12. The fixed bed fischer-tropsch iron catalyst activation pretreatment process of any one of claims 1 to 8, wherein each step is carried out at a reduction pressure of from 0.5 to 3.0 MPa.